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-   -   transmitter question - its a dousy (https://www.radiobanter.com/homebrew/21844-transmitter-question-its-dousy.html)

Ashhar Farhan December 9th 03 04:57 PM

If you want to put up a signal that covers a wide band, you will
essentially need a spreading function. In your case, there is no
corelation that will de-spread the signal at the receiving end, now,
regardless of the technique you employ to achieve this transmission,
one thing is sure, you will need some really heavy power.

imagine that you can cover 300 meters using a 10mW transmitter. Now,
this transmission is received by a receiver with a selectivity of
about 50KHz. If you were to cover such a signal every 50KHz for 1MHz,
you will require 1000/50 = 20 times as much power, that is, about
500mW. Correspondingly, if you wanted to transmit over a 10MHz
bandwidth, you will require 5Watts output to achieve the same result.

Now, lets move onto the next part: what kind of modulation? Frequency
modulation requires that the carrier should shift. Therefore, if you
modulated broadband noise, it wouldn't do. You will have to put out
carriers every 50KHz. This will require a comb generator. Hers is how,
pass the carrier through an XOR gate and feed the other input of the
XOR gate with a 50KHz carrier. This will keep flipping the phase by
180% and generate sidebands. The strength of the side bands will
depend upon how square your 50KHz carrier is. The carrier can be
frequency modulated as normally done.

This is a quick and dirty method. there are a number of problems with
this approach, first, there is really no way of limiting the signals
to a particular band unless you do extensive amount of filtering at
the output. second, the signals will be the strongest in the center
and taper off exponentially (not really, but actually) towards the
edges of the band.

Steve Nosko December 9th 03 06:15 PM

This needs clarification. Do you mean that it will generate multiple
carriers? Like this?

At the same time the output has carriers @ 88.1 and 88.3 and 88.5 and
88.7.....97.5 and 97.7 and 97.9 ????

Actually this is possible if you
can make the proper circuitry. An oscillator FM modulated with a 200 KHz
signal will do it. You just need enough deviation. You could also add in
the audio modulation.

Forgot to mention that I've done it.

Steve

k;9;d;c;i

"duckman" wrote in message
...
Had a question for open discussion

Is there available, can it be done to have an AM and/ and or FM

transmitter
that will broadcast over the entire AM and FM broadcast band at the same
time. Or at least multiple stations. E.G.

From 88 - 108 at once or 88-98, then 98-108
Same on AM band.

It would have to be a low power to be able to be used on private property
and limiy range to 300 mtrs

Can this be done, where can l buy it, or how do l make it

Told you it was a dousy of a question, whats your thoughts.





Steve Nosko December 9th 03 06:15 PM

This needs clarification. Do you mean that it will generate multiple
carriers? Like this?

At the same time the output has carriers @ 88.1 and 88.3 and 88.5 and
88.7.....97.5 and 97.7 and 97.9 ????

Actually this is possible if you
can make the proper circuitry. An oscillator FM modulated with a 200 KHz
signal will do it. You just need enough deviation. You could also add in
the audio modulation.

Forgot to mention that I've done it.

Steve

k;9;d;c;i

"duckman" wrote in message
...
Had a question for open discussion

Is there available, can it be done to have an AM and/ and or FM

transmitter
that will broadcast over the entire AM and FM broadcast band at the same
time. Or at least multiple stations. E.G.

From 88 - 108 at once or 88-98, then 98-108
Same on AM band.

It would have to be a low power to be able to be used on private property
and limiy range to 300 mtrs

Can this be done, where can l buy it, or how do l make it

Told you it was a dousy of a question, whats your thoughts.





Dana Myers December 11th 03 05:36 AM

duckman wrote:
Had a question for open discussion

Is there available, can it be done to have an AM and/ and or FM transmitter
that will broadcast over the entire AM and FM broadcast band at the same
time. Or at least multiple stations. E.G.

From 88 - 108 at once or 88-98, then 98-108
Same on AM band.

It would have to be a low power to be able to be used on private property
and limiy range to 300 mtrs

Can this be done, where can l buy it, or how do l make it

Told you it was a dousy of a question, whats your thoughts.


Conceptually, you're describing something similar to
ODFM, used in 802.11(a) and (g). Basically, you create
numerous independently modulated carriers across a band,
combine them and amplify them. If you're intent on
transmitting the same information on each carrier, then I
suppose a simplifying trick might be to produce a comb,
but the general case is basically identical to something
that exists already.

Now, here's a question that follows - suppose you built
an ODFM transmitter that was able to place a signal on
each 'channel' in the FM broadcast band. What could
power-level/signal-strength would be permitted under
Part 15? Would the aggregate ODFM signal be considered a
single signal for Part 15 purposes, or would each 'channel'
be considered an independent signal (since, technically, it
is)?


Dana

Dana Myers December 11th 03 05:36 AM

duckman wrote:
Had a question for open discussion

Is there available, can it be done to have an AM and/ and or FM transmitter
that will broadcast over the entire AM and FM broadcast band at the same
time. Or at least multiple stations. E.G.

From 88 - 108 at once or 88-98, then 98-108
Same on AM band.

It would have to be a low power to be able to be used on private property
and limiy range to 300 mtrs

Can this be done, where can l buy it, or how do l make it

Told you it was a dousy of a question, whats your thoughts.


Conceptually, you're describing something similar to
ODFM, used in 802.11(a) and (g). Basically, you create
numerous independently modulated carriers across a band,
combine them and amplify them. If you're intent on
transmitting the same information on each carrier, then I
suppose a simplifying trick might be to produce a comb,
but the general case is basically identical to something
that exists already.

Now, here's a question that follows - suppose you built
an ODFM transmitter that was able to place a signal on
each 'channel' in the FM broadcast band. What could
power-level/signal-strength would be permitted under
Part 15? Would the aggregate ODFM signal be considered a
single signal for Part 15 purposes, or would each 'channel'
be considered an independent signal (since, technically, it
is)?


Dana

Circuit Breaker December 30th 03 05:33 PM

duckman wrote:
something suspicious


I've been to about 5 different radio related groups this morning lurking
for information about a problem I have in a similar field to this duckman
guy, and (1) his request has been -- identically worded, if not mistaken
-- in each of the groups I've read, a couple related to pirate radio, a
couple related to professional broadcast radio, and a couple related to
ham radio. What gives?

Anywhoo, I've got a similar question I post shortly.

I know someone who has a desire for a piece of equipment that does the
same thing, but his reasoning is for people who blast their radios while
going down the street. It would be merely for shutting them up -- after
all, the person blaring the radio is usually the only one who wants to
hear it.

Anyway, 73 de KE4EDD

--
__ ____
/ _| | _ \ Unregistered Linux User #18,000,002
| |__ | _ \
\__/ |___/ Learning is the ONLY substitution for EDUCATION!


Circuit Breaker December 30th 03 05:33 PM

duckman wrote:
something suspicious


I've been to about 5 different radio related groups this morning lurking
for information about a problem I have in a similar field to this duckman
guy, and (1) his request has been -- identically worded, if not mistaken
-- in each of the groups I've read, a couple related to pirate radio, a
couple related to professional broadcast radio, and a couple related to
ham radio. What gives?

Anywhoo, I've got a similar question I post shortly.

I know someone who has a desire for a piece of equipment that does the
same thing, but his reasoning is for people who blast their radios while
going down the street. It would be merely for shutting them up -- after
all, the person blaring the radio is usually the only one who wants to
hear it.

Anyway, 73 de KE4EDD

--
__ ____
/ _| | _ \ Unregistered Linux User #18,000,002
| |__ | _ \
\__/ |___/ Learning is the ONLY substitution for EDUCATION!


Ghost Writer December 30th 03 06:08 PM

Ah YES..... I'd LOVE to come up with a device to blow out those extra loud
car systems. HOW RIDICULOUS they are. Aside from such a device, the next
good idea is invest in any companies making hearing aids. They WILL be
JUMPING IN STOCK in about 5 years. Any names come to mind? I'd like to start
looking. G.W.


"Circuit Breaker" wrote in message
. ..
I know someone who has a desire for a piece of equipment that does the
same thing, but his reasoning is for people who blast their radios while
going down the street. It would be merely for shutting them up -- after
all, the person blaring the radio is usually the only one who wants to
hear it.

Anyway, 73 de KE4EDD





Ghost Writer December 30th 03 06:08 PM

Ah YES..... I'd LOVE to come up with a device to blow out those extra loud
car systems. HOW RIDICULOUS they are. Aside from such a device, the next
good idea is invest in any companies making hearing aids. They WILL be
JUMPING IN STOCK in about 5 years. Any names come to mind? I'd like to start
looking. G.W.


"Circuit Breaker" wrote in message
. ..
I know someone who has a desire for a piece of equipment that does the
same thing, but his reasoning is for people who blast their radios while
going down the street. It would be merely for shutting them up -- after
all, the person blaring the radio is usually the only one who wants to
hear it.

Anyway, 73 de KE4EDD





Circuit Breaker December 30th 03 06:16 PM

Ghost Writer wrote:

Ah YES..... I'd LOVE to come up with a device to blow out those extra loud
car systems. HOW RIDICULOUS they are. Aside from such a device, the next
good idea is invest in any companies making hearing aids. They WILL be
JUMPING IN STOCK in about 5 years. Any names come to mind? I'd like to start
looking. G.W.


;-) Google for: hearing aid "Mel Tillis"

--
__ ____
/ _| | _ \ Unregistered Linux User #18,000,002
| |__ | _ \
\__/ |___/ Learning is the ONLY substitution for EDUCATION!



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